How Disney must be wishing this week that the technology used in Tron: Legacy to make Jeff Bridges appear as a younger version of his hoary old self, hadn't been as dodgy as the Millennium Falcon's hyperdrive. With all the talk of Harrison Ford, Mark Hamill and Carrie Fisher reprising their roles as Han Solo, Luke Skywalker and Princess Leia in a proposed new Star Wars trilogy (which now looks like it will be conceived by the Oscar-winning screenwriter of Toy Story 3 and Little Miss Sunshine, Michael Arndt), a CGI youthifying gizmo would have saved everybody a lot of time and hassle. The new film might start a few years after Return of the Jedi with each of the main characters still in fine fettle, and let them loose on the enemy with lightsabers and other non-Jedi-specific weapons swinging, as virile and lissom as ever.

Unfortunately, what just about worked for a movie that took place mostly inside a computer-generated world, would be yet more heresy for Star Wars fans. Those poor creatures are still recovering from George Lucas's preposterous efforts a few years ago to "update" his original trilogy with random, poorly placed additional CGI monsters and aliens. That's not to mention the clunky pixel-generated horrors of the prequel trilogy. So Disney are stuck with a trio who are 70 (Ford), 61 (Hamill) and 56 (Fisher) respectively – not exactly the ideal demographic to enthral a new generation of Jedi freaks. And if Luke, Leia and Han aren't going to be at the centre of the action, you have to wonder what the point is in including them at all.

So far, there has been no suggestion from the new owners of Lucasfilm that the forthcoming trilogy is a reboot, so we have to assume it takes place after Return of the Jedi chronologically, in a universe in which our heroes are either long dead or still living. This is a different challenge to that faced recently by rival series Star Trek, which was forced to recast and rejuvenate all its iconic characters while maintaining the interest and support of fans who adored the previous iterations. JJ Abrams et al turned what appeared to be a major hamstring into a spectacular advantage by bringing an older version of Spock (played by original cast member Leonard Nimoy) back through time to meet his younger self. While this shifted the series' canonical values somewhat, it made for a perfect launch vehicle that also managed to engage the older generation.

Star Wars is blocked from taking a similar route, but there are nevertheless lessons to be learned from Abrams' cleverness. It was regularly reported during the build-up to Star Trek that original Captain Kirk William Shatner was extremely upset not to have been offered at least a cameo, with the director forced to politely explain that the film-makers could find no workable way to include him. The reality, of course, is that one cult icon was quite enough to keep the Trekkies happy, while two or more might have upset the balance of the movie and left little room for the new cast of Star Trek to make their mark.

The same must inevitably be true of Star Wars. If the creative team behind the new trilogy want to deliver a debut film that revives the series without rebooting, they must bring us a new selection of characters that we care about as much as Luke, Leia and Han. The return of more than one of the latter trio (unless via the briefest of cameos) would swamp the new movie; and unfortunately for Harrison Ford fans, it makes no sense at all for Solo to be the one who gets the nod.

At the end of Return of the Jedi, Luke has come into the full range of his Force-fuelled powers, and any new Star Wars film that takes place in the imminent wake of the debut trilogy's events must inevitably involve the galaxy's one remaining Jedi Knight. Hamill in wise old Obi-Wan Kenobi mode would be the perfect earnest foil for the younger generation of budding Jedis (hopefully not too young) who might spearhead the action in the new movie. While Solo's character was vital to piercing the murky fog of pseudo-spiritual gubbins that surrounded Luke's rise to prominence, he was very much a supporting character in the grand scheme of things, and one cannot imagine him having matured much over the intervening decades. In fact, we would not want him to. He would make a pretty odd sort of mentor.

Just as Abrams chose Nimoy's gentle, statesmanlike Spock to return in Star Trek over a Shatner who would have sucked up all the available oxygen from the room, Disney needs to avoid the kind of iconic figure who could well expect to be given centre stage. In any case, if Disney needs a Solo-like charismatic scoundrel for the new series, there is a ready-made younger replacement in the form of Firefly's Nathan Fillion. Ford should be left in the green room.

Who would you cast in the new series, and would you bring back Luke, Leia and Han, or leave them to enjoy their well-earned retirements?